CVE-2019-9754 in Tiny C Compiler
Summary
by MITRE
An issue was discovered in Tiny C Compiler (aka TinyCC or TCC) 0.9.27. Compiling a crafted source file leads to an 1 byte out of bounds write in the end_macro function in tccpp.c.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2019-9754 represents a critical memory safety issue within the Tiny C Compiler version 0.9.27, a lightweight C compiler designed for rapid compilation and embedding purposes. This flaw manifests as an out-of-bounds write condition that occurs during the preprocessing phase of compilation when handling specially crafted source code files. The Tiny C Compiler, while widely used for embedded systems development, cross-compilation tasks, and as a teaching tool due to its minimal footprint and simplicity, becomes susceptible to memory corruption when processing malformed input. The vulnerability specifically targets the preprocessor component of TCC, which is responsible for handling macro expansions and other preprocessing directives before the actual compilation process begins.
The technical implementation of this vulnerability occurs within the end_macro function located in the tccpp.c source file, which manages the termination of macro processing operations. When a maliciously constructed source file is compiled, the function fails to properly validate array bounds during memory allocation or manipulation operations, resulting in a one-byte write beyond the allocated memory buffer. This type of out-of-bounds write represents a classic buffer overflow condition that can potentially be exploited to overwrite adjacent memory locations, corrupt program state, or in severe cases, enable arbitrary code execution. The vulnerability stems from inadequate input validation and boundary checking mechanisms within the macro processing subsystem, which is classified under CWE-121 as a stack-based buffer overflow due to the nature of the memory corruption occurring in the function's local variables or stack memory regions.
The operational impact of CVE-2019-9754 extends beyond simple compilation failures, as it introduces potential security risks that could be leveraged by attackers in various scenarios. Attackers could craft malicious source code files that, when processed by TCC, would trigger the out-of-bounds write condition, potentially leading to system compromise through memory corruption attacks. The vulnerability affects any system utilizing TCC 0.9.27 for compiling code, including development environments, build systems, and embedded applications where TCC serves as the primary compilation tool. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for executing malicious code through compiler-based attacks, as the compromised compiler could be used to generate malicious binaries or to exploit other system vulnerabilities through the corrupted compilation process.
Mitigation strategies for this vulnerability primarily involve immediate software updates to versions of TCC that have addressed the memory safety issue through proper boundary checking and input validation. System administrators and developers should prioritize upgrading to patched versions of the compiler, as the vulnerability represents a clear threat to compilation environments. Additionally, implementing runtime protections such as stack canaries, address space layout randomization, and memory protection mechanisms can help detect or prevent exploitation attempts. Input sanitization practices should be enforced when processing source code from untrusted sources, including the implementation of static analysis tools to identify potentially malicious code patterns before compilation. Organizations using TCC in automated build environments should also consider implementing compilation sandboxing techniques to limit the potential impact of exploitation attempts, ensuring that even if an attacker successfully triggers the vulnerability, the damage remains contained within a restricted execution environment.